Circular-cylinder sieve

ABSTRACT

In a cylindrical sieve, a first frame  7  is provided with a first ring plate  7   a  arranged in a radial direction and a ring plate  7   b  extended inward in an axial direction X of the sieve from an inner end of the first ring plate  7   a.  The ring plate  7   b  has an inwardly warped end. A ring projection  2   a  is fit in a ring-shaped cavity K 1  defined by a ring recess  10   a  and the first frame  7.  The ring plate  7   b  presses the ring projection  2   a  inward in the radial direction to prevent the ring projection  2   a  from being slipped off the matching recess. Through holes  7   c  (counter bores) are formed in the first frame  7  along the axial direction X. Four of the through holes  7   c  are used to fasten the rods  6  and receive the Phillips head screws  6   f  seated therein, and the remaining through holes  7   c  receives Phillips head screws  20  (see FIG.  1 ) seated therein for reinforced linkage of the first frame  7  with the holder frame  11.

TECHNICAL FIELD

The present invention relates to a cylindrical sieve used in acylindrical sieve-type particulate sifter for removal of foreignsubstances and for removal and crush of particulate lumps andaggregates.

BACKGROUND ART

Contamination of food with foreign substances and food poisoning aresome of major social problems. The term HACCP has recently becomefamiliar to even general consumers. The principal of HACCP is totalmanagement for safety and health in (food) manufacturing processes. Thecomprehensive countermeasures including designs of plants, manufacturingequipment and devices, and delivery are required for the totalmanagement. There is a manufacturing standard called GMP (GoodManufacturing Practice) for improvement in manufacturing environmentsand health to effectively prevent contamination of the manufacturingenvironments with offending substances. Compliance with the GMP standardto achieve the goals of the HACCP plans has been highly demanded. TheGMP standard mainly focuses safety management of employees and plantsand process management, but also has a requirement that machines andequipment are to be ‘designed adequately for cleaning’. In foodindustries, there are various measures to ensure safety handling ofparticulate materials and prevent contamination with foreign substancesin particulate supply equipment.

The foreign substances as potential contamination of the particulateproducts include metal pieces, glass pieces, gravels, plastic pieces,hairs, wood pieces, paper pieces, little pieces of thread, and rubberpieces. These foreign substances may be mixed both in a material supplyprocess as those present in a row material and in a manufacturing step.These foreign materials may be mixed also in a manufacturing step.

Various particulate supply systems are used in food plants according totheir scales, ranging, for example, from manual feed into blenders andother processing devices in small plants, to auto bag-opening and toauto measurement and auto particulate supplies from silos in big plants.There are accordingly diverse process steps in the food plants, forexample, a stock process, a measurement process, an auto bag-openingprocess, a manual feed process, a pneumatic conveying process, a foreignsubstance removal process, and a dust elimination process. The manualfeed process has a high potential for contamination with foreignsubstances in the manufacturing area required to have strict cleanness.Such facilities are to be improved promptly also from the viewpoint ofthe workers' safety.

In the pneumatic conveying system, zoning is allowed between aparticulate supply area and a food production area. A sifter or magnetslocated between the two areas can be used to remove foreign substancesor insect pests mixed in particulate materials. Additionally, one batchof the particulate material can be kept for the next process and thusthe working efficiency can be improved by using a dumping server(manual-feed pneumatic conveying device) or a pneumatic conveyingreceiver also as a storage bin.

There are possibilities of ‘exterior contamination with foreignsubstances’ and ‘interior generation of foreign substances’ in thedevices of the respective process steps, and various countermeasureshave been proposed.

In order to prevent ‘exterior contamination with foreign substances’,the whole line should be designed to be full-automatic and fully closed.If this is not practical, strict zoning tactics should be adopted toprevent contamination with foreign substances.

It is often assumed that the particulates are dry and are thus notsuitable for propagation of microorganisms even if the particulates arefood. Under certain conditions, however, dew condensation may occur inthe line (especially in the stock step) to cause propagation ofmicroorganisms and trigger ‘interior generation of foreign substances’.The aggregates and lumps of particulates may breed insect pest. Thepossible countermeasures against this problem are ‘thorough cleaning ofparts with a high potential for adhesion of particulates to make a deadstock’, ‘adequate design and selection of devices with little potentialfor adhesion and accumulation of particulates’, and ‘minimized dewcondensation due to a temperature difference in devices’.

Cylindrical sifters are generally used to prevent contamination withforeign substances and to remove and crush aggregates and lumps ofparticulates. The cylindrical sifters include inline sifters (see, forexample, WO 02/38290A1 and Japanese Patent Laid-Open Gazette No.H-6-321335) and non-inline sifters (see, for example, Japanese PatentLaid-Open Gazette No. H-3-131372, No. H-11-244784, No. S-63-69577, No.H-6-303, and No. S-57-12278). Recently developed have beenhigh-performance sifters that have blades on a shaft rotating at a highspeed in a cylindrical sieve for forcible sieving.

Diverse cylindrical sieves have been developed to be adopted in suchcylindrical sifters.

[Patent Document 1] Japanese Utility Model Laid-Open Gazette No.S-60-95986

This invention provides a sieve mounting structure adopted in acylindrical sifter 1. A mounting frame 2, to which sieves 3 and 21 aremounted, is formed in a substantially cylindrical shape and includes twocircular end frames 5 located on both ends in a bus direction S and alinkage frame 7 extended in the bus direction S for linkage of the twoend frames 5. The sieves 3 and 21 have lock elements 9 and 22 providedon both ends thereof in the bus direction S. A large number of throughholes 10 and 28 are made between the lock elements 9 and 22. The lockelements 9 and 22 of the sieves 3 and 21 are attached to the end frames5 by means of fixing elements 4 and 23. The sieves 3 and 21 are strainedin the bus direction S inside the mounting frame 2. The mounting frame 2also includes intermediate frames 6 and 25 that are located between theend frames 5 and are joined with the end frames 5 via the linkage frame7. The lock elements 9 and 22 of the sieves 3 and 21 are mounted on theintermediate frames 6 and 25 via the fixing elements 4 and 23. Theintermediate frames 6 and 25 have a smaller diameter than the diameterof the end frames 5 and are gradually tapered. Rubber cushions 14 areinterposed between the sieves 3 and 21 and the intermediate frames 6 and25.

In this prior art structure, the sieves 3 and 21 are attached withtension to the end frames 5 of the mounting frame 2 by means of thefixing elements 4 and 23 having screws, washers, and nuts. Thisstructure lessens the number of attachments and facilitates the mountingoperation. The most areas of the sieves 3 and 21 except the areas closeto the lock elements 9 and 22 and the seams exert the sieving functionand have practically smooth surface. This ensures the smooth flow ofobject particulates to be processed without causing localized abrasion.Tension of the strained attachment prevents slacks and thus preventsclogging of the sieves having even low rigidity, making the processedparticulates flow smoothly.

The prior art structure disclosed in Patent Document 1, however, stillhas some drawbacks as discussed below:

(1) The sieves 3 and 21 are fastened to the end frames 5 of the mountingframe 2 by the fixing elements 4 and 23 and are strained throughadjustment of the screws. It is practically impossible to set theperfectly even clamping force of the fixing elements over thecylindrical faces of the sieves. There is naturally a variation intension over the faces of the sieves 3 and 21. The varying tension maycause slacks of the sieves 3 and 21. For example, the areas close to thescrews may be tightly strained, while the residual areas may be ratherloose. The local clamping of the sieves 3 and 21 with the fixingelements may deform the sieves 3 and 21 to have wavy edges. Namely onlyskilled workers can successfully strain the sieves to set relativelyeven tensions over the sieves, whereas unskilled workers may have afailure and time-consuming post-adjustment may be required).

There are high-performance cylindrical inline sifters that have bladeson a shaft rotating at a high speed in the sieve for forcible sieving.The slacks of the sieves 3 and 21 may cause the rotating blades to comeinto contact with and damage the sieves 3 and 21.

(2) Attachment and detachment of the screws of the fixing elements 4 and23 are rather time-consuming and make replacement of the sieves 3 and 21troublesome. Fixation of the sieves 3 and 21 having the larger diameterby the fixing elements 4 and 23 is often beyond one worker's control.

By taking into account the drawbacks of the prior art structurediscussed above, the cylindrical sieve of the invention aims to enableeven an unskilled worker to easily equalize the tension over the sieveby simple operations without causing any slack and to enable only oneworker to easily replace even a large net member.

DISCLOSURE OF THE INVENTION

The present invention is directed to a cylindrical sieve, whichincludes: a cylindrical net member that has ring projections provided onboth ends thereof; multiple bar members of a preset length that areextended in an axial direction; a first ring member that is providedwith first lock elements fixed to or fit in respective one ends of thebar members; a second ring member that is provided with second lockelements fixed to or fit in respective other ends of the bar members;and a pair of holder ring members that are located between the firstring member and the second ring member to be movable along the multiplebar members and have ring recesses. The ring projections are set in thering recesses, and the holder ring members are respectively brought intocontact with the first ring member and with the second ring member. Thefirst lock elements and the second lock elements work to prevent thering projections from being slipped off the ring recesses. The holderring members are respectively fastened to the first ring member and tothe second ring member by means of fixation elements.

The cylindrical sieve disclosed in claim 1 desirably eliminates thedrawbacks of the prior art structure.

In the cylindrical sieve of the invention, the multiple bar members havethe fixed length, and the cylindrical net member is clamped between theadjoining ring members by means of the ring projections provided on bothends of the net member. This structure enables even an unskilled workerto evenly apply the tension over the net member and accordingly preventsany potential slack of the net member due to a local difference intension.

The ring projections of the net member are fastened by the first ringmember, the second ring member, and the holder ring members. Thisstructure enables only one worker to easily replace even a large netmember.

The net member may be made of any of diverse materials includingsynthetic resins and metals. Available materials of the net memberinclude meshes (for example, polyester meshes, nylon meshes, andstandard steel (SS) or stainless steel (SUS) meshes), punching metalswith a large number of apertures perforated therein, and integrallymolded synthetic resins with a large number of openings. The apertureratio is set in a generally acceptable range but is preferably not lessthan 40%. Each of the ring projections may be formed, for example, tohave a circular cross section or a rectangular cross section or to behollow.

The frame structure except the net member is preferably designed toforbid disassembly. The varying intervals between the adjoining framesfor fastening the net member may undesirably cause a variation intension over the net member.

It is preferable that the net member is divided into multiple pieces.

That is, the present invention is also directed to a cylindrical sieve,which includes: a cylindrical first net member that has ring projectionsprovided on both ends thereof; a cylindrical second net member that hasring projections provided on both ends thereof; multiple bar members ofa preset length that are extended in an axial direction; a first ringmember that is fixed to or fit in respective one ends of the barmembers; a second ring member that is fixed to or fit in respectiveother ends of the bar members; an intermediate ring member that is fixedto middle sections of the bar members; a pair of first holder ringmembers that are located between the first ring member and theintermediate ring member to be movable along the multiple bar membersand have ring recesses; and a pair of second holder ring members thatare located between the intermediate ring member and the second ringmember to be movable along the multiple bar members and have ringrecesses. The ring projections of the first net member are set in thering recesses of the first holder ring members, and the first holderring members are respectively brought into contact with the first ringmember and with the intermediate ring member. The first holder ringmembers are respectively fastened to the first ring member and to theintermediate ring member by means of fixation elements. The ringprojections of the second net member are set in the ring recesses of thesecond holder ring members, and the second holder ring members arerespectively brought into contact with the intermediate ring member andwith the second ring member. The second holder ring members arerespectively fastened to the intermediate ring member and to the secondring member by means of fixation elements.

In one preferable embodiment, each of the first ring member, the secondring member, and the intermediate ring member has a first ring platearranged in a radial direction and a second ring plate extended in theaxial direction from the first ring plate. Each of the ring projectionsis set in a ring-shaped cavity defined by the ring recess, the firstring plate, and the second ring plate. The second ring plate holds downthe ring projection inward in the radial direction and accordinglyprevents the ring projection from being slipped off the ring-shapedcavity.

In another preferable embodiment, the fixation elements are nuts, whichare screwed and set on male screws formed on the bar members to berelatively movable in the axial direction.

In still another preferable embodiment, the ring projections havecircular or rectangular cross sections in the axial direction and aremade of a material having a sufficient hardness to hold their circularor rectangular shapes when being fit in the ring recesses.

The ring projections made of the material having the sufficient hardnessto hold their original shapes facilitate fixation to the frame structureof the sieve.

In one preferable arrangement, the net member is surrounded by themultiple bar members, the first ring member, the second ring member, andthe holder ring members.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a cylindrical sieve in a firstembodiment of the invention;

FIG. 2 is a partially enlarged perspective view showing an intermediateframe of the cylindrical sieve;

FIG. 3A is a front view of a first net member;

FIG. 3B is a front view of a modified example of the first net member;

FIG. 3C is a side view showing a main net body of the first net member;

FIG. 3D is a front view showing a net member made of a hard material;

FIG. 4 is a center-vertical sectional view of the cylindrical sieve;

FIG. 5 is an end-vertical sectional front view showing a first frame ofthe cylindrical sieve;

FIG. 6 is an end-vertical sectional front view showing a second frame ofthe cylindrical sieve;

FIG. 7 is an end-vertical sectional front view showing the intermediateframe of the cylindrical sieve;

FIG. 8A is a left side view of the first frame;

FIG. 8B is a front view of the first frame;

FIG. 8C is an end-sectional front view of the first frame;

FIG. 9A is a left side view of the second frame;

FIG. 9B is a front view of the second frame;

FIG. 9C is an enlarged view showing a circumferential part of FIG. 9A;

FIG. 9D is an end-sectional front view of the second frame;

FIG. 10 is a left side view of the intermediate frame;

FIG. 10B is a front view of the intermediate frame;

FIG. 10C is an end-sectional front view of the intermediate frame;

FIG. 11A is a left side view of a holder frame;

FIG. 11B is a front view of the holder frame;

FIG. 11C is an end-sectional front view of the holder frame;

FIGS. 12A and 12B show assembly method of the cylindrical sieve;

FIG. 13 is a center-vertical sectional view showing a cylindrical sifterwith the cylindrical sieve attached thereto; and

FIG. 14 is a perspective view showing another cylindrical sieve in asecond embodiment of the invention.

BEST MODES OF CARRYING OUT THE INVENTION

A cylindrical sieve 1 in one embodiment of the invention is discussedbelow with reference to FIGS. 1 through 7. The cylindrical sieve 1includes a cylindrical first net member 3 with a pair of ringprojections 2 a and 2 b formed on both ends thereof, a cylindricalsecond net member 5 with a pair of ring projections 4 a and 4 b formedon both ends thereof, multiple (four in this embodiment) rods 6 of afixed length extended in an axial direction X, a circular ring-shapedfirst frame 7 fixed to a face perpendicular to the axial direction X onrespective one end sections 6 a of the rods 6, a circular ring-shapedsecond frame 8 fixed to a face perpendicular to the axial direction X onrespective other end sections 6 b of the rods 6, and a circularring-shaped intermediate frame 9 fixed to a face perpendicular to theaxial direction X on middle sections 6 c of the rods 6. The cylindricalsieve 1 further includes a pair of circular ring-shaped first holderframes 11 and 12 that are positioned between the first frame 7 and theintermediate frame 9 to be movable along the rods 6, have ring recesses10 a and 10 b formed by methods such as ditching, and are arranged onfaces perpendicular to the axial direction X to be movable and fixablein the axial direction X, and a pair of circular ring-shaped secondholder frames 14 and 15 that are positioned between the intermediateframe 9 and the second frame 8 to be movable along the rods 6, have ringrecesses 13 a and 13 b, and are arranged on faces perpendicular to theaxial direction X to be movable and fixable in the axial direction X.

The ring projections 2 a and 2 b of the first net member 3 are fit inthe ring recesses 10 a and 10 b of the first holder frames 11 and 12.The first holder frames 11 and 12 are respectively brought into contactwith and fastened to the first frame 7 and to the intermediate frame 9by means of fixation elements 16 and 17 (for example, nuts). Theinterval between the first frame 7 and the second frame 8, the intervalbetween the first frame 7 and the intermediate frame 9, and the intervalbetween the intermediate frame 9 and the second frame 8 are respectivelyset to fixed lengths.

The ring projections 4 a and 4 b of the second net member 5 are fit inthe ring recesses 13 a and 13 b of the second holder frames 14 and 15.The second frames 8 are respectively brought into contact with theintermediate frame 9 and the second frame 8, and the second holderframes 14 and 15 are respectively fastened to the intermediate frame 9and the second frame 8 by means of fixation elements 18 and 19.

The cylindrical sieve 1 is preferably made of stainless steel, althoughthe first net member 3 and the second net member 5 may be composed ofsynthetic resin, instead of stainless steel. The total dimensions of thecylindrical sieve 1 are unchanged, regardless of attachment anddetachment of the first and second net members 3 and 5.

The respective elements of the cylindrical sieve 1 are described indetail.

The first net member 3 is formed to have a cylindrical shape as shown inFIGS. 3A through 3C. The first net member 3 may be made of any materialhaving sufficient flexibility and plasticity, such as synthetic resin(for example, polyester) and may be obtained by netting or by integralmolding. The dimensions of the first net member 3 may be determinedarbitrarily according to the applications.

The first net member 3 has a main net body 3 a with the ring projections2 a and 2 b attached to the outer circumference of both ends thereof.

The material of the main net body 3 a of the first net member 3 is notrestricted at all, and the form of the main body 3 a may be a mesh or apunching plate. The aperture ratio of the first net member 3 may beselected arbitrarily according to the requirements, but is preferably ina range of 40 to 66%. One preferable example of the main net body 3 a ismade of polyethylene terephthalate (PET) and has a mesh of 30.5, anopening of 0.6, a wire diameter of 0.245, and an aperture ratio of 51%.

As shown in FIG. 3B, the ring projections 2 a and 2 b are frames made ofsynthetic resin (for example, vinylon). A doubled joint band element 2 fis extended from each of the opening of the circular section of 2 a and2 b. And each end of the main net body 3 a is clamped between thedoubled joint band and sewed therebetween. Each of the ring projections2 a and 2 b has a frame having circular cross section along the axialdirection X and a sufficient hardness to hold the circular shape whenbeing fit in the matching recess as discussed later. The ringprojections 2 a and 2 b may be hollow or may alternatively havering-shaped core reinforcements.

FIG. 3C shows the main net body 3 a. The main net body 3 a is designedto have a seam in an inverse direction to a rotating direction of bladesset in a cylindrical sifter (not shown). The rotating direction of theblades is reversed corresponding to the orientation of a particulateinlet.

The second net member 5 has the identical structure with that of thefirst net member 3. The above description and illustration regarding thefirst net member 3 is thus also applied to the second net member 5.

Similarly the ring projections 4 a and 4 b are identical with the ringprojections 2 a and 2 b, so that the above description and illustrationregarding the ring projections 2 a and 2 b is also applied to the ringprojections 4 a and 4 b.

FIG. 3D shows a cylindrical net member 3 m made of a flexible hardmaterial, such as metal mesh or punching metal. Rectangular or circularrings 2 m are fixed to specific areas of an outer circumference on bothends of a main net body 3 n. The aperture ratio of the first net member3 may be selected arbitrarily according to the requirements, but ispreferably in a range of 44 to 55%. One preferable example of thecylindrical net member 3 m is made of stainless steel and has a mesh of16, an opening of 1.09, a wire diameter of 0.5, and an aperture ratio of47.1%.

As shown in FIG. 4, the first net member 3 is surrounded by the rods 6,the first frame 7, the second frame 8, the first holder frames 11 and12, and the second holder frames 14 and 15. The respective frames 7, 8,11, 12, 14, and 15 are arranged coaxially and preferably havesubstantially identical inner diameters and outer diameters.

Referring to FIG. 5, the one end section 6 a of each rod 6 has a basescrewed into a rod element 6 d and fastened and welded to the rodelement 6 d via a nut 6 e and a head forming a Phillips head screw 6 f.Similarly the other end section 6 b of each rod 6 has a base screwedinto a rod element 6g and fastened and welded to the rod element 6 g viaa nut 6 h and a head forming a Phillips head screw 6 i.

Both ends of the middle section 6 c are screwed into the rod elements 6d and 6 g and are fastened and welded to the rod elements 6 d and 6 gvia nuts 6 j and 6 k.

As shown in FIGS. 5 and 8, the first frame 7 has a first ring plate 7 aarranged in a radial direction and a ring plate 7 b extended inward inthe axial direction X from an inner end of the first ring plate 7 a. Thering plate 7 b has an inwardly warped end to protect the first netmember 3 from damages. The ring projection 2 a is fit in a ring-shapedcavity K1, which is defined by the ring recess 10 a and the first frame7 and has a ring-shaped opening P1. The ring plate 7 b pressingly holdsdown the ring projection 2 a inward in the radial direction to preventthe ring projection 2 a from being slipped off the matching recess. Thering-shaped cavity K1 is designed to be greater in size than the ringprojection 2 a. The ring recess 10 a is formed in an L shape with anupwardly (inwardly) extended free end but is not restricted to theillustrated structure. This is because an opening width of thering-shaped opening P1 is designed to be smaller than the diameter ofthe ring projection 2 a, and the ring projection 2 a has a circularcross section along the axial direction and is made of the materialhaving the sufficient hardness to hold the circular shape when being fitin the matching recess. The first frame 7 has multiple through holes 7 c(counter bores) formed in the axial direction X. Four of the throughholes 7 c are used to fasten the rods 6 and receive the Phillips headscrews 6 f seated therein. The remaining through holes 7 c receivePhillips head screws 20 (see FIG. 1) seated therein for reinforcedlinkage of the first frame 7 with the holder frame 11.

As shown in FIGS. 6 and 9, the second frame 8 has a first ring plate 8 aarranged in the radial direction and a ring plate 8 b extended inward inthe axial direction X from an inner end of the first ring plate 8 a. Thering plate 8 a has an inwardly warped end to protect the first netmember 5 from damages. The ring projection 4 b is fit in a ring-shapedcavity K2, which is defined by the ring recess 13 b and the second frame8 and has a ring-shaped opening P2. The ring plate 8 b pressingly holdsdown the ring projection 4 b inward in the radial direction to preventthe ring projection 4 b from being slipped off the matching recess. Thisis because an opening width of the ring-shaped opening P2 is designed tobe smaller than the diameter of the ring projection 4 b,and the ringprojection 4 b has a circular cross section along the axial directionand is made of the material having the sufficient hardness to hold thecircular shape when being fit in the matching recess. The second frame 8has multiple (six in this embodiment) through holes 8 c (counter bores)formed in the axial direction X. Four of the multiple through holes 8 bare used to fasten the rods 6 and receive the Phillips head screws 6 iseated therein. The remaining through holes 8 c receive the Phillipshead screws 20 (see FIG. 1) seated therein for reinforced linkage of thesecond frame 8 with the holder frame 15. The second frame 8 also hasinner handles 8 d and outer guide projections 8 e provided for easyattachment to the cylindrical sifter (not shown). The guide projections8 e are fit in grooves (not shown) formed in the cylindrical sifter (notshown). The cylindrical sieve 1 with the handles 8 d held with theworker's hands is pressed into and is thereby fixed in the cylindricalsifter (not shown).

As shown in FIGS. 7 and 10, the intermediate frame 9 has a first ringplate 9 a fixed (welded in this embodiment) to tapped center areas ofthe middle sections 6 c of the respective rods 6 and arranged in theradial direction and a second ring plate 9 b extended in the axialdirection X on both sides of the first ring plate 9 a. The ringprojection 2 b and the ring projection 4 a are respectively fit in aring-shaped cavity K3, which is defined by the ring recess 10 b, thefirst ring plate 9 a, and the second ring plate 9 b and has aring-shaped opening P3, and in a ring-shaped cavity K4, which is definedby the ring recess 13 a, the first ring plate 9 a, and the second ringplate 9 b and has a ring-shaped opening P4. The second ring plate 9 apressingly holds down the ring projections 2 b and 4 a inward in theradial direction to prevent the ring projections 2 b and 4 a from beingslipped off the matching recesses. This is because opening widths of therespective ring-shaped openings P3 and P4 are designed to be smallerthan the diameters of the corresponding ring projections 2 b and 4 a,and the ring projections 2 b and 4 a have circular cross sections alongthe axial direction and are made of the material having the sufficienthardness to hold the circular shapes when being fit in the matchingrecesses. The intermediate frame 9 has multiple (four in thisembodiment) through holes 9 c formed in the axial direction X.

As shown in FIGS. 5 and 11, the first holder frame 11 has the ringrecess 10 a arranged outside in the axial direction X and multiple (fourin this embodiment) through holes 11 a. The respective one end sections6 a of the rods 6 run through these through holes 11 a (see FIG. 5). ThePhillips head screws 20 (see FIG. 1) are screwed into multiple (four inthis embodiment) screw holes 11 b of the first holder frame 11. Thesecond holder frames 14 and 15 have similar structures with the ringrecesses 10 a and 10 b arranged opposite to each other.

The second holder frames 14 and 15 have similar structures to those ofthe first holder frames 11 and12. The above description and illustrationregarding the first holder frame 11 is thus also applied to the secondholder frames 14 and 15.

The fixation elements 16, 17, 18, and 19 are nuts to be screwed and setonto the male threads formed on the outer circumferences of the rods 6to be relatively movable in the axial direction X. The fixation elements16 to 19 function as stoppers of the holder frames 11, 12, 14, and 15.The loosened fixation elements 16 to 19 enable the holder frames 11, 12,14, and 15 to freely move along the rods 6.

Assembly of the cylindrical sieve 1 of this embodiment is described withreference to FIG. 12. The assembly process first clamps the first netmember 3 between the first frame 7 and the first holder frame 11. Thering projection 2 a is inserted into an inner end area by takingadvantage of the flexibility of the first net member 3 as shown in FIG.12A. The holder frame 11 is slid leftward in the drawing to receive thering projection 2 a in the ring-shaped cavity K1, which is defined bythe ring recess 10 a and the inner end wall of the first frame 7. Theholder frame 11 is fastened to the first frame 7 via the fixationelements 16. A left vertical plane of the holder frame 11 is broughtinto contact with a right vertical plane of the first frame 7, so thatthe ring projection 2 a is closed and retained in the ring-shaped cavityK1. The linkage of the holder frame 11 with the first frame 7effectively prevents the ring projection 2 a from being slipped off thering-shaped cavity K1. The ring recess 10 b on the other end of thefirst net member 3 is received and retained in the ring-shaped cavity K2in a similar manner, so the above description is also applied to thispart.

The loosened fixation elements 16 enable the first net member 3 havingthe sufficient flexibility to be drawn out according to the reverseprocedure for replacement. A new first net member 3 of the sufficientflexibility is inserted into the inner space of the framework of thecylindrical sieve 1 and is securely fastened according to the aboveprocedure.

The second net member 5 is fastened and replaced in a similar manner tothat of the first net member 3. The above description is thus alsoapplied to the second net member 5.

As described above, the ring projections 2 a, 2 b, 4 a, and 4 b areclamped between the adjoining ring frames and are securely fastened. Theholder frames 11, 12, 14, and 15 apply the overall fixation force to setthe even tension onto the net members 3 and 5. The cylindrical sieve 1manufactured in accurate dimensions enables even a non-skilled worker tostrain the net members 3 and 5 with the even tension. The holder frame11, 12, 14, and 15 uniformly press the net members 3 and 5 without anytension-affecting elements, such as screws and bands, so as to apply theeven tension.

The cylindrical sieve of this embodiment is applicable to an inlinesifter disclosed in WO 02/38290A1 as shown in FIG. 13.

An inline sifter 101 shown in FIG. 13 includes a particulate-air mixturereceiver unit 103 that receives pneumatically conveyed particulate-airmixture, a particulate-air mixture inlet 104 of a circular tube that isconnected with the particulate-air mixture receiver unit 103 andsupplies the particulate-air mixture conveyed from an upstream line viaan upstream blower and an upstream rotary valve (not shown) to theparticulate-air mixture receiver unit 103, and a sifter module 105 thathas an inner space horizontally communicating with the inner space ofthe particulate-air mixture receiver unit 103 fixed on one end thereof.The inline sifter 101 also includes a rotating shaft 106 that isextended horizontally in the particulate-air mixture receiver unit 103and the sifter module 105, a tubular sieve 107 that is set in the siftermodule 105, a booster 108 that is integrated with the rotating shaft 106and is extended in a rotatable manner inside the sieve 107 to increasethe air flow, an access door 109 that is provided in the sifter module105 for removal of aggregates and lumps caught on the sieve 107 and forinternal inspection, an outlet joint pipe 110 that is provideddownstream the sifter module 105 and discharges the particulates passingthrough the sieve 107 to a downstream line, and a motor 111 that drivesand rotates the rotating shaft 106.

The particulate-air mixture receiver unit 103 includes a cylindricalfeed casing 130, a cylindrical feed chamber 131 that communicates withthe particulate-air mixture inlet 104 that is connected to the outercircumference of the feed casing 130 in a tangentially inclined manner,a bearing chamber 132 that receives bearings therein, a partition wall133 that separates the feed chamber 131 from the bearing chamber 132,and a shaft hole 134 that is formed in the partition wall 133 to receivethe rotating shaft 106 therein. The particulate-air mixture receiverunit 103 also includes a first bearing 135 that is set in the shaft hole134 to support the rotating shaft 106 in a rotatable manner, a secondbearing 136 that is positioned on a left end portion of theparticulate-air mixture receiver unit 103 and supports the rotatingshaft 106 in a rotatable manner at a position closer to the shaft endthan the first bearing 135, and a conduit 137 that feeds theparticulate-air mixture into the sifter module 105. The first bearing135 and the second bearing 136 are provided as cartridges, and the firstbearing 135 has non-illustrated labyrinth ring and air purge. Theposition of the particulate-air mixture inlet 104 relative to the feedchamber 131 is preferably in the tangential direction of the outer wallof the feed casing 130 and has, for example, an inclination angle of 45degrees. The position of the particulate-air mixture inlet 104 may bevaried to have the inclination angle in a range of 0 to 90 degrees.

The sifter module 105 includes a shifter casing 150 that has an inverseU-shaped side view and a larger diameter than that of the particulatemixture receiver unit 103, a sifter process chamber 151 that is locatedinside the sifter casing 150 and communicates with the feed chamber 131,and a hopper-shaped particulate-air mixture outlet 152 that is providedbelow the sifter casing 150. The cylindrical sieve 1 of the embodimentis arranged coaxially in the sifter process chamber 151 to receive therotating shaft 106 passing through the center thereof. An inner area 153of the sieve 1 communicates with the feed chamber 131. The sifterprocess chamber 151 has a double cylindrical structure having the innerarea 153 and an outer area 154 separated by the sieve 1. The outletjoint pipe 110 is connected to the lower end of the particulate-airmixture outlet 152.

The rotating shaft 106 has a cantilevered bearing structure with itsfree end extended to the vicinity of the right end of the sieve 1 insidethe sifter process chamber 151.

The sieve 1 is designed to have an inner diameter substantiallyidentical with the inner diameter of the feed casing 130 and a lengthapproximately equal to the length of the sifter process chamber 151. Thesieve 1 is detachably attached to the sifter casing 150 by means of asieve fixation element 155.

The booster 108 is arranged outside the rotating shaft 106 and isextended in the inner area 153 of the sieve 1. The booster 108 hasmultiple (two in this example) radial elements 181 that are provided onboth ends of the rotating shaft 106 in the area of the sieve 1, blades182 that are fit in and fastened to the respective ends of the radialelements 181 and are extended to have a slight inclination (for example,in a range of 3 to 7 degrees and more specifically 5 degrees) relativeto the axial direction of the rotating shaft 106, and plate scrapers 183that are attached to at least part of the blades 182 and are a littleprojected outward in the radial direction from the blades 182 to makesome clearances against the inner wall of the sieve 1 for scraping outthe particulates from the inner area 153 to the outer area 154 via thesieve 1. The booster 108 has a pi (π) front shape and a cross-like sideshape.

A preset number (four in this example) of the blades 182 aresymmetrically arranged at specified angles in profile (90 degrees inthis example). The blades 182 may be curved slightly on both endsthereof or may be straight. Each blade 182 has a long plate-like frontshape.

The access door 109 is attached to and detached from a right sideopening 13 of the sifter casing 150 by means of multiple mounting knobs115. The access door 109 has two handles 116 set symmetrically againstthe center thereof and enables the sieve 1 to be removed through theside opening 113. Access windows 118 and 119 are formed on the center ofthe access door 109 and in the front section of the sifter casing 150 toenable the worker to visually check the inside of the sifter casing 150.

The motor 111 is driven to integrally rotate the rotating shaft 106 andthe booster 108. A continuous supply of the particulate-air mixturethrough the particulate-air mixture inlet 104 in the tangentialdirection into the feed chamber 131 forcibly flows into the sifterprocess chamber 151 to reach the inner area 153 of the sieve 7.

The booster 108 is rotated at a high speed with rotation of the rotatingshaft 106 inside the sieve 1, and the blades 182 and the radial elements181 of the booster 108 accordingly stir the particulate-air mixture.Stirring of the particulate-air mixture with the blades 182 of thebooster 108 effectively removes and crushes the lumps and aggregates ofthe particulates. The blades 182 also scratch off the lumpedparticulates accumulated on the nets of the sieve 1. The particulate-airmixture of the finer particulates than the mesh opening of the sieve 1is accordingly fed to the outer area 154 and is flown into thedownstream line via the outlet joint pipe 110, while the largerparticulates and foreign substances than the mesh opening of the sieve 1remain in the inner area 153.

The continuous operation of the inline sifter 101 naturally causesaccumulation of the larger particulates and foreign substances in theinner area 153. The worker occasionally checks the inside of the inlinesifter 101 through the access windows 118 and 119. When removal of theparticulates and the foreign substances is required, the worker stopsthe operation of the inline sifter 101, loosens the mounting knobs 115of the access door 109, and opens the access door 9 with the handles116. The worker can thus gain access to the inside of the sifter processchamber 151 and remove the remaining particulates and foreign substancesto clean the inside of the sieve 1 up. As for replacement of the sieve1, the sieve 1 is detached from the sifter process chamber 151 and a newsieve is inserted into the same place. As for cleaning of the sieve 1,the sieve 1 is detached from the sifter process chamber 151 and isinserted into the same place after cleaning.

The cylindrical sieve 1 of the embodiment described above has thefollowing advantages:

(1) The multiple rods 6 have the fixed length. The net members 3 and 5are clamped between the adjoining frames 7, 8, 9, 11, 12, 14, and 15 bymeans of the ring projections 2 a, 2 b, 4 a, and 4 b provided on therespective ends of the net members 3 and 5. This structure enables evenan unskilled worker to evenly apply the tension over the net members 3and 5 and accordingly prevents any potential slack of the net members 3and 5 due to a local difference (variation) in tension.

(2) The ring projections 2 a, 2 b, 4 a, and 4 b of the net members 3 and5 are fastened by the frames 7, 8, 9, 11, 12, 14, and 15. This structureenables only one worker to easily replace even large net members.

(3) The simple structure of the embodiment separates the prior artsieves 3 and 21 into multiple pieces but still desirably lowers thetotal manufacturing cost of the net members 3 and 5.

(4) The ring projections 2 aa, 2 b, 4 a, and 4 b are not exposed to theoutside. The multiple-frame structure has good appearance, as well asthe high functionality.

In the structure of the first embodiment, the net members 3 and 5 areseparated by the intermediate frame 9. The structure of a secondembodiment shown in FIG. 14 has an integral net member 203, instead ofthe separate net members, and accordingly excludes the ring projection 2b, the ring projection 4 a, the intermediate frame 9, the ring recess 10b, the first holder frame 12, the ring recess 13 a, the second holderframe 14, the fixation elements 17 and 18, the nuts 6 e and 6 h, themiddle sections 6 c, the nuts 6 j and 6 k, the first ring plate 9 a, thesecond ring plate 9 b, the ring-shaped cavity K3, the ring-shaped cavityK4, and the through holes 9 c. This structure is adoptable for arelatively short cylindrical sieve 201. The structure of the secondembodiment exerts the similar effects to those of the first embodiment.

The embodiments discussed above are to be considered in all aspects asillustrative and not restrictive. There may be many modifications,changes, and alterations without departing from the scope or spirit ofthe main characteristics of the present invention. All changes withinthe meaning and range of equivalency of the claims are thereforeintended to be embraced therein.

The structure of the above embodiment has only one intermediate frame 9,but multiple intermediate frames preferably having substantiallyidentical diameter may be included in the sieve structure. Thearrangement of the invention is applicable to cylindrical sifters ofboth a vertical structure and a horizontal structure. The Phillips headscrews 6 f and 6 i used to fasten the rods 6 to the frames 7 and 8 arenot restrictive at all and may be replaced by, for example, hexagonsocket head bolts. The number of rods used in the sieve structure is notrestricted to four but may be six or any other suitable number accordingto the diameter of the sieve structure. Assembly of the sieve structureand replacement of the net members may be executed with the sievestructure standing or lying.

1. A cylindrical sieve, which includes: a cylindrical net member thathas ring projections provided on both ends thereof; multiple bar membersof a preset length that are extended in an axial direction; a first ringmember that is provided with first lock elements fixed to or fit inrespective one ends of said bar members; a second ring member that isprovided with second lock elements fixed to or fit in respective otherends of said bar members; and a pair of holder ring members that arelocated between said first ring member and said second ring member to bemovable along said multiple bar members and have ring recesses, whereinsaid ring projections are set in said ring recesses, and said holderring members are respectively brought into contact with said first ringmember and with said second ring member, said first lock elements andsaid second lock elements work to prevent said ring projections frombeing slipped off said ring recesses, and said holder ring members arerespectively fastened to said first ring member and to said second ringmember by means of fixation elements.
 2. A cylindrical sieve, whichincludes: a cylindrical first net member that has ring projectionsprovided on both ends thereof; a cylindrical second net member that hasring projections provided on both ends thereof; multiple bar members ofa preset length that are extended in an axial direction; a first ringmember that is fixed to or fit in respective one ends of said barmembers; a second ring member that is fixed to or fit in respectiveother ends of said bar members; an intermediate ring member that isfixed to middle sections of said bar members; a pair of first holderring members that are located between said first ring member and saidintermediate ring member to be movable along said multiple bar membersand have ring recesses; and a pair of second holder ring members thatare located between said intermediate ring member and said second ringmember to be movable along said multiple bar members and have ringrecesses, wherein said ring projections of said first net member are setin said ring recesses of said first holder ring members, said firstholder ring members are respectively brought into contact with saidfirst ring member and with said intermediate ring member, and said firstholder ring members are respectively fastened to said first ring memberand to said intermediate ring member by means of fixation elements, andsaid ring projections of said second net member are set in said ringrecesses of said second holder ring members, said second holder ringmembers are respectively brought into contact with said intermediatering member and with said second ring member, and said second holderring members are respectively fastened to said intermediate ring memberand to said second ring member by means of fixation elements.
 3. Acylindrical sieve in accordance with either claim 1, wherein each ofsaid first ring member, said second ring member, and said intermediatering member has a first ring plate arranged in a radial direction and asecond ring plate extended in said axial direction from said first ringplate, and each of said ring projections is set in a ring-shaped cavitydefined by said ring recess, said first ring plate, and said second ringplate, and said second ring plate holds down said ring projection inwardin said radial direction and accordingly prevents said ring projectionfrom being slipped off said ring-shaped cavity.
 4. A cylindrical sievein accordance with claim 1, wherein said fixation elements are nuts,which are screwed and set on male screws formed on said bar members tobe relatively movable in said axial direction.
 5. A cylindrical sieve inaccordance with claim 1, wherein said ring projections have circular orrectangular cross sections in said axial direction and are made of amaterial having a sufficient hardness to hold their circular orrectangular shapes when being fit in said ring recesses.
 6. Acylindrical sieve in accordance with claim 1, wherein said net member issurrounded by said multiple bar members, said first ring member, saidsecond ring member, and said holder ring members.